Air-space insulated electric cable



Oct. 1, 1940. s. NEHMIZ ET AL.

AIR-SPACE INSULATED ELECTRIC CABLE Filed Nov. 22, 1937 Patented Oct. 1, 1940 2,216,419 AIB- SPACE INSULATED ELECTRIC CABLE Gerhard Nehmiz, Berlin, and Erich Budie, Potsdam, Germany,

many

assignors to Norddeutsche Kabelwerke Aktlengesellschatt, Berlin,

Ger-

Appllcatlon November 22, 1937, Serial No. 175:936

In Germany December 3, 1936 4 Claims.

This invention relates to an air-space insulated electric cable, more particularly a high-frequency cable.

It has already been proposed in an air-space insulated electric cable to support the central conductor in relation to the outer conductor or covering by .means of threads. For this purpose the outer conductor or covering has been produced in the form of a braided hollow cylinder, single threads of which were passed about the central conductor during the braiding operation. A cable of this character cannot be produced on existing spinning and twisting machines. It has also been proposed in air-space insulated 1 electric cables to support the conductor situated within a hollow cylindrical covering by a plurality of threads conducted in diametrical opposition from the outer covering to the conductor.

In this embodiment it has furthermore been proposed to, employ an open helical winding consisting of one single tape. This cable, however,

is also so complicated to produce that it has no significance in practice.

It is the object of the invention to improve generally on cables of this character, and to devise an air-space insulated high-frequency electric cable, which can be produced readily on existing machines, and in the accomplishment of this object and also other objects and advantages which will become apparent as the description proceeds the invention comprises an air-space insulated electric cable in which the helically wound tape constituting the outer conductor or covering is furnished with marginal recesses, which are disposed at an angle to the longitudinal direction of the tape and are adapted to receive the thread or threads supporting the central conductor.

The supporting thread is wound with a pitch which is shorter than that of the tape, thepoints of support of the central conductor then being disposed in close proximity to one another and the supporting thread being almost vertical to the central conductor. This disposal is particularly favourable, both from the electrical as well as the mechanical point of view. 1

In place of one supporting thread there may also be employed a plurality of threads, which are either situated close together or are so distributed over the width of the helical tape winding that they are located at approximately equal distances apart. In the latter case there is obtained the most uniform radial support of the central conductor. If desired, the suppor ng thread can also be separately secured on the helical tape winding, as the thread is disposed along the tape winding.

If recesses are provided along the edge of the tape in short succession to one another, the supporting thread when wound about the tape 5 will always find a suitable supporting point.

In a specific embodiment of the invention the tape possesses a U-shaped cross-section. The flanges or limbs of the U are furnished with recesses adapted to receive the supportingthread. m In this embodiment the supporting thread can be secured by a separate tape which, resting between the flanges of the U, is wound over the tape having the recesses.

The marginal recesses can also be formed by 15 providing the tape with a sectional form disposed at an angle to the longitudinal axis of the tape corresponding to the pitch of the supporting thread. It is also possible to provide merely the marginal zone of the tape with a shaped sec-' 20 tional form. In the embodiments described in the above the helically wound tapemay consist of metal or also of a synthetic or other nonmetallic material. The provision of a shaped sectional form has the advantage that the tape then 2 possesses a greater mechanical strength as compared with a flat tape.

When winding a sectionally shaped tape composed of a thermoplastic synthetic material the tape is heated to an extent sufficient to permit 30 of the requisite deformation. After the helical winding has been produced the tape must again be cooled before the application of the supporting thread.

The invention is illustrated diagrammatically 35 by way of example in the accompanying drawing, in which Fig. 1 shows a section of electric cable according to the invention.

Fig. 2 shows a modified embodiment of the cable.

' Fig. 3 shows a piece of the tape having the marginal recesses employed for the outer con ductor or covering.

Fig. 4 is a plan view of a piece of tape having a 'U-shaped cross-section.

Fig. 5 is a cross-section taken along the line V--V in Fig. 4.

Fig. (i is a plan view of one form of shaped w sectional tape.

Fig. 7 is a cross-section of the tape according to Fig. 6.

Fig. 8 shows an additional embodiment o shaped sectional tape.

Fig. 9 is a cross-section of the tape according to Fig. 8.

In Fig. 1, l is the central conductor, which is supported within the outer covering or conductor by threads 2. This outer covering comprises a helically wound tape 3 having recesses l. The supporting thread for the central conductor is introduced into the recesses 4, as clearly shown by the drawings.

In the embodiment according to Fig. 2 the cable likewise comprises the central conductor I, the helically wound tape 3 having the recesses 4, and the supporting thread 2. As shown by the drawing, the supporting thread 2 possesses, as compared with the embodiment in Fig. 1, a shorter pitch than the outer covering 3. The supporting thread 2 is introduced into the recesses l in the tape 3, but it will be clearly seen from Fig. 2 that in this case the points at which the central conductor 1 is supported are disposed a comparatively short distance apart. Fig. 2 also shows that the supporting thread is practically vertical in its approach towards the central conductor, having the advantages referred to in the above.

Fig. 3 shows the provision of the recesses I at the edges of a flat tape 3. In Figs. 4 and 5 the tape possesses a U-shaped cross-section, and the recesses 4 are provided in the flanges 5. In this embodiment the supporting thread can be secured by a separate tape 6 which, as shown in Fig. 5, is wound into the trough of the U-shaped tape, so that the thread 2 passes between the tape 6 and the web of the tape 3 and is held and maintained in a taut condition by the tape 6.

Figs. 6 and 7 show a sectional tape, in which the profile runs obliquely, i. e-., at an angle to the longitudinal direction of the tape corresponding to the pitch of the supporting thread. This embodiment clearly shows that there may also be used a plurality of supporting threads.

As shown by Figs. 8 and 9, it is also possible to provide merely the marginal zones of the tape with a distinct sectional form.

The embodiments-according to Figs. 6 to 9 have the advantage that the supporting thread is securely guided over those portions of its length where it contacts with the helically wound tape. Owing to the obliquely disposed profile there are produced at the same time the recesses adapted to receive the thread.

In practice it will be found desirable to provide over the helical winding an additional winding wound in the opposite direction in order to secure the first winding against axial displacement.

What we claim as new and desire to secure by Letters Patent is:

1. In an air-space insulated electric cable, a central conductor, an outer covering comprising a helically wound tape having recesses disposed at least along both longitudinal edges of the tape, and at least one supporting thread alternately passing about the central conductor and over the said tape and lying in said recesses, the said recesses being so disposed that the pitch of the said thread when supported in the said recesses is smaller than the pitch of the helically wound tape.

2. In an air-space insulated electric cable, a central conductor, an outer covering comprising a helically wound tape 01' fiat form having recesses extending into the plane of the tape along both longitudinal edges thereof, and at least one supporting thread alternately passing about the central conductor and over the said tape and lying in said recesses, the said recesses being so disposed that the pitch of the said thread when supported in the said recesses is smaller than the pitch of the helically wound tape.

3. In an air-space insulated electric cable, a central conductor, an outer cover comprising a helically wound tape of shaped sectional form having recesses sunk into the thickness of the tape and extending obliquely from the one longitudinal edge of the tape to the other, and at least one supporting thread alternately passing about the central conductor and over the said tape and lying in said recesses, the said recesses being so disposed that the pitch of the said thread when supported in the said recesses is smaller than the pitch of the helically wound tape.

4. In an air-space insulated electric cable, a central conductor, an outer cover comprising a helically wound tape of shaped sectional form having recesses sunk into the thickness of the tape in zones extending along the two longitudinal edges thereof and disposed obliquely to the longitudinal direction of the tape, and at least one supporting thread alternately passing about the central conductor and over the said tape and lying in said recesses, the said recesses being so disposed that the pitch of the said thread when supported in the said recesses is smaller than the pitch of the helically wound tape.

ERICH BUDIE. GERHARD NEHlVIIZ. 

